Measuring and comparing explosive forces.

[Traab]

Ok, this is something I would like clarification of. In a lot of situations, such as screw attacks death battles, they talk about how much tnt it would take to equal the destructive power they are using as a feat. For example, punching a mountain so hard it shatters. What i want to know is, does the explosive force required to explode said mountain equal the same amount of force a piercing attack that shatters it? An explosion is expanding in all directions, therefore isnt a lot of the force not being applied to said target? To use explosive comparisons, a bunker buster versus a normal missile. The bunker buster is designed to penetrate before exploding, so doesnt it have far less explosive force needed to do the same job as a conventional weapon would need to do the same thing?

In some cases, such as the character unleashing a shockwave or something, a direct comparison to explosives makes sense. This question came to mind watching Luffy from One Piece practice his new technique by punching solid steel walls easily several feet thick and causing massive dents about the size of a human torso in diameter and warping the entire plate with every blow. Eventually shattering this chunk of steel probably 12 feet high and 4 feet thick. Somebody in the comment section was saying that this is the kind of force comparable to city destroying bombs to create similar effects. So i wondered if thats a reasonable comparison to use explosives to measure the power behind a tightly contained blow. If the amount of force an explosion would require to match the effect means thats how much force his fist was unleashing.

[Strigon]

I can't say for certain what Death Battle uses as their metric (though I think you're probably reading too much into them, as for all they claim to be about genuine analysis, their choices end up being largely arbitrary), you are definitely correct in saying that "destructive force" is a rather wishy-washy term, especially when comparing different types of attacks.

The only reasonable way I can see to directly compare those different attacks (short of directly comparing their effects, such as "how much steel can it penetrate?") is just by measuring the pressure they apply. Even then, there are times when total force would be more useful than pressure, and times when pressure would be more useful than total force.
Mostly this is because "destructive force" isn't really a thing, as an object can be destroyed in many different ways, and is uniquely resistant to every single one.

[Traab]

I can't say for certain what Death Battle uses as their metric (though I think you're probably reading too much into them, as for all they claim to be about genuine analysis, their choices end up being largely arbitrary), you are definitely correct in saying that "destructive force" is a rather wishy-washy term, especially when comparing different types of attacks.

The only reasonable way I can see to directly compare those different attacks (short of directly comparing their effects, such as "how much steel can it penetrate?") is just by measuring the pressure they apply. Even then, there are times when total force would be more useful than pressure, and times when pressure would be more useful than total force.
Mostly this is because "destructive force" isn't really a thing, as an object can be destroyed in many different ways, and is uniquely resistant to every single one.

Generally what they do is say, "Here is how much tnt exploding it would take to do comparable damage" Leveling a mountain range, blowing up a planet, shattering the multiverse so hard it turns marvel into dc, there is a tnt figure for it. And yeah I know death battle isnt actually a science based group using actual physicists to determine things like that, I just wondering if using the explosive force of tnt was even a useful metric for some case, such as the one I mentioned with luffy punching torso sized dents into solid steel. Im sure there IS an explosive force that could do that, but im not sure if explosive force would be the same as whatever type of force luffy is applying and thus equal in level.

[theNater]

Force is force, so it is comparable. While you're right that setting off that much TNT next to the steel plate probably wouldn't create that dent, there are ways to turn explosive force into impact force. A cannon, for example, takes the explosive force of gunpowder and turns it into the impact force of a cannonball strike. "How big of an explosion would you need to propel a fist-sized cannonball hard enough to leave that dent?" is basically the question they're answering.

[Yora]

It's not just force that matters, but also the amount of time for which the force is applied, and the area over which it is applied.
Classic example is firing handheld guns. The bullet is going to hit the target with the same amount of force as the grip is pushing on your hand, or the stock at your shoulder. Bur a pistol grip is pushing on a much larger surface on your hand than the area where the bullet hits the target. And I think because of innertia, the more massive gun is accelerating much slower than the lighter bullet.
Or as another example, you can push an egg with a golf club slowly along the ground for a hundred meters or basically forever. But if you try to swing and hit the egg with just enough force to push it a distance of 10 meters, it will simply shatter. Even though the total amount of force is much lower than what's needed to push the egg for a hundred meters.

Even with explosives there are different categories. There are different explosives to shatter material and to push material.

[sktarq]

okay one of the issues here is that when in the real world things are being measured in TNT equivalents is not a force measurement, its energy. A ton of TnT is 4.189 x 10⁹Joules if one wants get fussy.
Because lets face it it mostly comes down to the fact that nuclear weapons are measured in tonnes of TNT...and so are other explosions regardless of source (fertilizer, a railcar of artillery shells, volcanism, sugar refinery/other particle suspension detonations, etc)

And force changes radically based on a number of factors including where the measurement is being taken, shape of the explosive material, surrounding materials (reflectors, absorbers, mixes, etc) and this can be radically variable for even a single explosion...so it is isn't a very useful metric, but "total energy released" is a simple measurement that transfers between scenarios rather well which is why it is used.

Now "total energy released" and "damage done" is not a 1:1 thing. There are lots and lots of factors that come into play. Entire fields of engineering have been born out of trying to understand these dynamics. So they only really become comparable if other factors are being controlled for....like a giant falling steel ball of 100m diameter vs one of 100m radius for example...or a nuke to a nuke, etc.

So I'd say "Death Battles" somewhat doesn't know what they are talking about or if they do what they do is measure how much energy it would take to make whatever change they want to measure and convert. But mostly I think they probably tossed an idea of "cool" "it makes people think of a punch as big as nuke!" and kinda left it at that.

[Strigon]

Or as another example, you can push an egg with a golf club slowly along the ground for a hundred meters or basically forever. But if you try to swing and hit the egg with just enough force to push it a distance of 10 meters, it will simply shatter. Even though the total amount of force is much lower than what's needed to push the egg for a hundred meters.

That's an example of impulse, not force. It isn't true to say that you're applying more force just because it's applied for a longer amount of time, because force is not measured with respect to time.

[gomipile]

The comparison with TNT is only a comparison of the approximate total energy required for a task. It isn't a precise measure of the size of bomb needed to do that task. The task might not even be possible or straightforward to do with a single bomb.

Take, for example, the idea that one could perfectly cook a chicken or other food item by setting off a nuclear bomb of a particular yield at a particular distance. Naiveley, one might intuit that there must be a combination of yield and distance that would work for a specific food item, but this isn't true in general. Cooking most types of food "perfectly" or any kind of properly requires an application of heat over a relatively long amount of time, which the explosion alone does not provide.

As another example, a dent of a particular shape in metal may be easy to make with one type of tool, but more difficult with a different type of tool. The shape and depth of dent produced by a particular choice of hammer with a given set of impact parameters may not be able to be replicated by a single simple explosion, and probably won't be in general. The energy, impulse, pressure, and force profiles applied over space and time are very different for these two types of tools.

Also, even within explosives, explosive charges of the same energy content can behave quite differently from each other. Different chemical compositions and mixtures of explosives have different properties. This thread has mostly been concerned with the energy of an explosion, which would related to the energy density of a particular explosive composition. But there are other important properties.

Another important property of industrial and military explosive mixtures is brisance. Oversimplified, this is similar to a measure of the pressure an explosive can create upon detonation. Different types of industrial uses can require low, high, or medium brisance.

Related but distinct is the detonation velocity of a material or mixture. This is important when timing is critical. Such as when producing a particular shape of shockwave with shaped charges, or when using detonation cord to link and time simultaneous or sequential charges.

That isn't even getting in to differences between devices loaded with similar charges, as referred to by the OP's mention of bunker busters, within which category alone there are many distinctions.

So, even a ton of TNT isn't necessarily a "ton of TNT" depending on specifics.